The influence of raw material contamination with mycotoxins on alcoholic fermentation indicators

Self-cascade deoxynivalenol detoxification by an artificial enzyme with bifunctions of dehydrogenase and aldo/keto reductase from genome mining

Due to the severe health risks for human and animal caused by the intake of toxic deoxynivalenol (DON) derived from Fusarium species, elimination DON in food and feed has been initiated as a critical issue. Enzymatic cascade catalysis by dehydrogenase and aldo-keto reductase represents a fascinating strategy for DON detoxification. Here, one quinone-dpendent alcohol dehydrogenase DADH oxidized DON into less-toxic 3-keto-DON and NADPH-dependent aldo-keto reductase AKR13B3 reduced 3-keto-DON into relatively non-toxic 3-epi-DON were identified from Devosia strain A6-243, indicating that degradation of DON on C3 are two-step sequential cascade processes. To establish the bifunctions, fusion enzyme linking DADH and AKR13B3 was successfully assembled to promote one-step DON degradations with accelerated specific activity and efficiency, resulting 93.29 % of DON removal rate in wheat sample. Three-dimensional simulation analysis revealed that the bifunctional enzyme forms an artificial intramolecular channel to minimize the distance of intermediate from DADH to AKR13B3 for two-step enzymatic reactions, and thereby accelerates this enzymatic process. As the first report of directing single step DON detoxification by an interesting bifunctional artificial enzyme, this work revealed a facile and eco-friendly approach to detoxify DON with application potential and gave valuable insights into execute other mycotoxin detoxification for ensuring food safety.

Biodegradation of Aflatoxin B1 in the Baijiu Brewing Process by Bacillus cereus

Aflatoxin is a potent mycotoxin and a common source of grain contamination that leads to great economic losses and health problems. Although distilled baijiu cannot be contaminated by aflatoxin, its presence in the brewing process affects the physiological activities of micro-organisms and reduces product quality. Bacillus cereus XSWW9 capable of degrading aflatoxin B1 (AFB1) was isolated from daqu using coumarin as the sole carbon source. XSWW9 degraded 86.7% of 1 mg/L AFB1 after incubation at 37 °C for 72 h and tolerated up to 1 mg/L AFB1 with no inhibitory effects. Enzymes in the cell-free supernatant of XSSW9 played a significant role in AFB1 degradation. The AFB1-degradation activity was sensitive to protease K and SDS treatment, which indicated that extracellular proteins were responsible for the degradation of AFB1. In order to investigate the AFB1-degradation ability of XSSW9 during the baijiu brewing process, AFB1 and XSWW9 were added to grain fermentation (FG-T) and normal grain fermentation without AFB1, while normal grain fermentation without AFB1 and XSWW9 was used as a control (FG-C). At the end of the fermentation, 99% AFB1 was degraded in the residue of fermented grains. The differences of microbial communities in the fermented grains showed that there were no significant differences between FG-T and FG-C in the relative abundance of dominant genera. The analysis of volatile compounds of their distillation showed that the contents of skeleton flavor components was similar between FG-T and FG-C. These results offer a basis for the development of effective strategies to reduce the effect of AFB1 on the brewing process and ensure that the production of baijiu is stable.

Profiling of Organic Compounds in Bioethanol Samples of Different Nature and the Related Fractions

Forty-one bioethanol real samples and related fractions, together with a biobutanol sample, have been analyzed with gas chromatography coupled to either mass spectrometry (GC-MS) or flame ionization detection (GC-FID). Bioethanol with different water contents, samples originated from several sources of biomass, first- as well as second-generation specimens, distillation fractions, samples stocked in containers made of four different materials, and, finally, a biobutanol sample have been analyzed. The number of the compounds found through GC-MS has been 130, including alcohols, aldehydes, ketones, esters, ethers, nitrogen compounds, organic acids, furane derivates as well as other species (e.g., limonene). Afterward, a quantitative determination of major components of bioethanol has been carried out. The achieved results have revealed that, besides ethanol and, in some cases, water, species such as acetaldehyde, methanol, and higher alcohols, as well as 1,1-diethoxyethane, may be present at concentrations above 500 mg L^-1. While the source of bioethanol (nature of the raw material, ethanol generation, or water content) has a direct impact on its volatile organic compound (VOC) profile, the material of the container where the biofuel has been stored does not play a significant role. Finally, the results have demonstrated that, for a given production process, different distillation fractions contain unequal VOC profiles.

The Aspergilli and Their Mycotoxins: Metabolic Interactions With Plants and the Soil Biota

Species of the highly diverse fungal genus Aspergillus are well-known agricultural pests, and, most importantly, producers of various mycotoxins threatening food safety worldwide. Mycotoxins are studied predominantly from the perspectives of human and livestock health. Meanwhile, their roles are far less known in nature. However, to understand the factors behind mycotoxin production, the roles of the toxins of Aspergilli must be understood from a complex ecological perspective, taking mold-plant, mold-microbe, and mold-animal interactions into account. The Aspergilli may switch between saprophytic and pathogenic lifestyles, and the production of secondary metabolites, such as mycotoxins, may vary according to these fungal ways of life. Recent studies highlighted the complex ecological network of soil microbiotas determining the niches that Aspergilli can fill in. Interactions with the soil microbiota and soil macro-organisms determine the role of secondary metabolite production to a great extent. While, upon infection of plants, metabolic communication including fungal secondary metabolites like aflatoxins, gliotoxin, patulin, cyclopiazonic acid, and ochratoxin, influences the fate of both the invader and the host. In this review, the role of mycotoxin producing Aspergillus species and their interactions in the ecosystem are discussed. We intend to highlight the complexity of the roles of the main toxic secondary metabolites as well as their fate in natural environments and agriculture, a field that still has important knowledge gaps.

The presence of ochratoxin A does not influence Saccharomyces cerevisiae growth kinetics but leads to the formation of modified ochratoxins

Yeasts are able to reduce the levels of ochratoxin A in fermentative processes; and, through their enzymatic complex, these micro-organisms are also capable of forming modified mycotoxins. These mycotoxins are often underreported, and may increase health risks after ingestion of contaminated food. In this sense, this study aims to evaluate whether the presence of ochratoxin A influences yeast growth kinetic parameters and to elucidate the formation of modified ochratoxin by Saccharomyces cerevisiae strains during fermentation. Three S. cerevisiae strains (12 M, 01 PP, 41 PP) were exposed to OTA at the concentrations of 10, 20 and 30 μg/L. The Baranyi model was fitted to the growth data (Log CFU/mL), and the identification of modified ochratoxins was performed through High Resolution Mass Spectrometry. The presence of ochratoxin A did not influence the growth of S. cerevisiae strains. Four pathways were proposed for the metabolization of OTA: dechlorination, hydrolysis, hydroxylation, and conjugation. Among the elected targets, the following were identified: ochratoxin α, ochratoxin β, ochratoxin α methyl ester, ochratoxin B methyl ester, ethylamide ochratoxin A, ochratoxin C, hydroxy-ochratoxin A, hydroxy-ochratoxin A methyl ester, and ochratoxin A cellobiose ester. These derivatives formed from yeast metabolism may contribute to the occurrence of underreporting levels of total mycotoxin in fermented products.

Influence of microbial and chemical contaminants on the yield and quality of ethanol from wheat grains

BACKGROUND

Higher alcohols and esters have a negative impact on ethanol quality; therefore, to analyze the influence of mycotoxins and pesticides on higher alcohols and esters formation during ethanol production from contaminated cereal grains is of outstanding importance.

RESULTS

In this study, the yield of ethanol and the composition of volatile by-products (acetaldehyde, methyl acetate, ethyl acetate, methanol, propanol, isobutanol, amyl and isoamyl alcohols) after fermentation of wheat grains artificially contaminated with Fusarium sporotrichioides and pesticides (triasulfuron and sulfosulfuron) were analyzed. Wheat grains contamination with triasulfuron significantly reduced ethanol yield and increased isobutanol and ethyl acetate content. Moreover, wheat grains infection with F. sporotrichioides significantly increased methyl acetate, ethyl acetate, isobutanol, and amyl and isoamyl alcohols content. Significant differences between pesticides and wheat variety on volatile compounds formation in ethanol has been estimated.

CONCLUSION

The results showed that grains contaminated with F. sporotrichioides and pesticides significantly influenced the process of alcoholic fermentation that leads to variation of by-products in ethanol, including higher alcohols, esters, and aldehydes. © 2018 Society of Chemical Industry.

Fusarium culmorum mycotoxin transfer from wheat to malting and brewing products and by-products

The objectives of this study were to establish the impact of Fusarium culmorum infection and fungicide treatment on the occurrence of deoxynivalenol (DON), 3-acetyl deoxynivalenol, T-2 toxin, HT-2 toxin, nivalenol, fusarenon-X, diacetoxyscirpenol and zearalenone in wheat, wheat malt and wort (beer). The concentrations of these compounds were also measured in the germ/rootlets, spent grains and spent yeast because these are the most important by-products and are further used as food or feed additives. Two wheat genotypes were obtained from the Agricultural Institute in Osijek, Croatia. The Osk.110/09 genotype, the genotype more susceptible to Fusarium infections, and Lucija, the genotype less susceptible to Fusarium, were analysed in this research. Each genotype was treated in four different ways at the field: (A) control, (B) treated with fungicide Prosaro® 250, (C) inoculated with F. culmorum spores and treated with fungicide Prosaro® 250, and (D) inoculated with F. culmorum spores. All samples were malted and brewed according to standard procedures, products and by-products were analysed for the mycotoxins by using LC-MS/MS. Since the majority of trichothecenes are polar molecules, the water after steeping was also analysed with LC-MS/MS. Mycotoxin concentrations were lower in malt samples treated with the fungicide. Elevated mycotoxin concentrations were observed in samples of both genotypes exposed to F. culmorum. Fungicide treatment was observed to suppress mycotoxin production and accumulation. However, samples with notably high mycotoxin concentrations, especially DON, retained elevated mycotoxin concentrations throughout the entire beer production process, even after a six-month storage period. DON proved to be the most frequently occurring mycotoxin in all of the by-products. The highest concentration of this compound was found in the steeping water from sample D (Osk.110/09), at 20,326 μg/l, leaving the spent grains of this sample with no detectable levels of DON.

From malt to wheat beer: A comprehensive multi-toxin screening, transfer assessment and its influence on basic fermentation parameters

The aim was to determine the mycotoxin transfer rate into beer during a semi-industrial production process and the effect of fungicide treatment in the field on mycotoxins concentrations in beer. To ensure the usual practical agronomical conditions, sample A was treated with fungicide Prosaro® 250, and sample B was infected with Fusarium culmorum spores, in order to obtain infected malt. Malt was produced using standard procedure and beer was produced in a semi-industrial unit. During fermentation measurement of sugars (maltotriose and maltose), glycerol and ethanol content was performed on a daily basis. Multiple toxins were determined in malt and beer. Deoxynivalenol (DON), its modified plant metabolite DON-3-glucoside (DON-glucoside), brevianamide F, tryptophol, linamarin, lotaustralin, culmorin (CUL), 15-hydroxy-CUL and 5-hydroyx-CUL were detected in all samples. Results indicate that F. culmorum infection did not influence the fermentation process or the alcohol concentration.

Properties and Fermentation Activity of Industrial Yeasts Saccharomyces cerevisiae, S. uvarum, Candida utilis and Kluyveromyces marxianus Exposed to AFB1, OTA and ZEA

In this paper the effect of aflatoxin B₁, ochratoxin A and zearalenon on morphology, growth parameters and metabolic activity of yeasts Saccharomyces cerevisiae, Saccharomyces uvarum, Candida utilis and Kluyveromyces marxianus was determined. The results showed that the three mycotoxins affected the morphology of all these yeasts, primarily the cell diameter, but not their final cell count. Fourier transform infrared spectroscopy showed that the yeast membranes bound the mycotoxins, C. utilis in particular. The cell membranes of most yeasts underwent denaturation, except S. uvarum exposed to ochratoxin A and zearalenone. In the early stage of fermentation, all mycotoxin-exposed yeasts had lower metabolic activity and biomass growth than controls, but fermentation products and biomass concentrations reached the control levels by the end of the fermentation, except for C. utilis exposed to 20 µg/mL of zearalenone. The adaptive response to mycotoxins suggests that certain yeasts could be used to control mycotoxin concentrations in the production of fermented food and beverages.

Mycotoxins and beer. Impact of beer production process on mycotoxin contamination. A review

Beer is the most consumed alcoholic beverage in the world. Its contamination with mycotoxins is of public health concern, especially for heavy drinkers. Beer production implies a variety of operations which might impact the initial level of mycotoxins in a positive or negative way. The complexity of these operations do not give to the brewer a complete control on chemical and biochemical reactions that take place in the batch, but the knowledge about mycotoxin properties can help in identifying the operations decreasing their level in foodstuffs and in the development of mitigation strategies. This review discusses available data about mycotoxin evolution during malting and brewing process. The operations that may lead to a decrease in mycotoxin load are found to be steeping, kilning, roasting, fermentation and stabilization operations applied over the process (e.g. clarification). Also, other general decontamination strategies usually employed in food industry, such as hot water treatment of barley, ozonation or even the use of lactic acid bacteria starter cultures during malting or fermentation are considered.

Mycotoxin Contamination in the EU Feed Supply Chain: A Focus on Cereal Byproducts

Mycotoxins represent a risk to the feed supply chain with an impact on economies and international trade. A high percentage of feed samples have been reported to be contaminated with more than one mycotoxin. In most cases, the concentrations were low enough to ensure compliance with the European Union (EU) guidance values or maximum admitted levels. However, mycotoxin co-contamination might still exert adverse effects on animals due to additive/synergistic interactions. Studies on the fate of mycotoxins during cereal processing, such as milling, production of ethanol fuels, and beer brewing, have shown that mycotoxins are concentrated into fractions that are commonly used as animal feed. Published data show a high variability in mycotoxin repartitioning, mainly due to the type of mycotoxins, the level and extent of fungal contamination, and a failure to understand the complexity of food processing technologies. Precise knowledge of mycotoxin repartitioning during technological processes is critical and may provide a sound technical basis for feed managers to conform to legislation requirements and reduce the risk of severe adverse market and trade repercussions. Regular, economical and straightforward feed testing is critical to reach a quick and accurate diagnosis of feed quality. The use of rapid methods represents a future challenge.

Fumonisins in conventional and transgenic, insect-resistant maize intended for fuel ethanol production: implications for fermentation efficiency and DDGS co-product quality

Mycotoxins in maize grain intended for ethanol production are enriched in co-product dried distiller's grains and solubles (DDGS) and may be detrimental to yeast in fermentation. This study was conducted to examine the magnitude of fumonisin enrichment in DDGS and to analyze the impacts of insect injury, Fusarium ear rot severity, and fumonisin contamination on final ethanol yield. Samples of naturally-contaminated grain (0 to 35 mg/kg fumonisins) from field trials conducted in 2008-2011 were fermented and DDGS collected and analyzed for fumonisin content. Ethanol yield (determined gravimetrically) was unaffected by fumonisins in the range occurring in this study, and was not correlated with insect injury or Fusarium ear rot severity. Ethanol production was unaffected in fumonisin B1-spiked grain with concentrations from 0 to 37 mg/kg. Bacillus thuringiensis (Bt) maize often has reduced fumonisins due to its protection from insect injury and subsequent fungal infection. DDGS derived from Bt and non-Bt maize averaged 2.04 mg/kg and 8.25 mg/kg fumonisins, respectively. Fumonisins were enriched by 3.0× for 50 out of 57 hybrid × insect infestation treatment combinations; those seven that differed were <3.0 (1.56 to 2.56×). This study supports the industry assumption of three-fold fumonisin enrichment in DDGS, with measurements traceable to individual samples. Under significant insect pest pressures, DDGS derived from Bt maize hybrids were consistently lower in fumonisins than DDGS derived from non-Bt hybrids.